In the U.S. Pat. No. 3,994,969, there is disclosed a process for the manufacture of salts of poly-alpha-hydroxyacrylic acids which contain monomeric units of the formula: ##STR2## in which R.sub.1 and R.sub.2 independently represent hydrogen or an alkyl group containing from 1 to 3 carbon atoms, and in which M represents the cationic radical resulting from the dissociation of a base, by reacting, with the corresponding base, in the presence of water, the solid polylactone derived from the corresponding poly-alpha-hydroxyacrylic acid in which process the reaction is carried out in a liquid medium containing a diluent, so that the polylactone and the salt produced do not dissolve in the medium.
However, it is difficult, in accordance with the process of U.S. Pat. No. 3,994,969, to obtain products having an optimum whiteness, which can be used directly as active adjuvants in detergent compositions, for example, in washing powders, or as sequestering agents.
In the manufacture of salts of non-hydroxylic carboxylic acid polymers of reduced molecular weight, it is known to neutralize the corresponding polycarboxylic acid which already has a low molecular weight. See U.S. Pat. No. 3,637,609 which concerns the fabrication of sodium polymaleate by neutralization of polymaleic acid. This process does not generally make it possible to obtain perfectly white products without a subsequent bleaching operation. Thus, in U.S. Pat. No. 3,637,609, the sodium polymaleate salt obtained by the neutralization is in the form of finely divided pale yellow particles which are then bleached with a bleaching agent such as hydrogen peroxide, peracetic acid, sodium hypochlorite, perbenzoic acid or ozone.